Build a Pass-Through Slot and Material Riser System for Cutting Oversized Stock on Your Laser Cutter

Every laser cutter has a bed size limit, and sooner or later a project shows up that's longer than your machine's Y-axis travel — a full sheet of plywood signage, a long batten, a strip of edge banding. Rather than buying a bigger machine, most diode and CO2 laser owners solve this with a pass-through setup: a slot cut into the machine's rear or side panel plus an external riser that holds the stock level with the bed, so material can hang out of the enclosure while you cut it in sections. This project walks through building a pass-through slot and riser system that works on enclosed diode lasers like the Ray5 in an enclosure, and on CO2 cabinet machines with a rear access panel.

How Pass-Through Cutting Actually Works

The trick isn't just cutting a hole in the case — it's keeping the working section of material perfectly level with the bed's existing surface on both sides of the slot, and keeping your design software honest about where each section actually is. You cut the design in tiles: position the stock, cut everything that fits within the travel area, then slide the material through the slot by a known, precisely measured distance and cut the next tile, repeating until you've covered the full length. LightBurn's array and file-splitting tools, or a properly measured manual offset in your design software, keep the tiles aligned so the seams don't show.

Difficulty and Planning Notes

This is a moderate build — mostly precise fabrication and careful measurement rather than anything electrically complex. The riser height is the part that actually matters: it has to match your bed height to within a millimeter or your focus will be off on the material hanging outside the machine, so measure your specific machine's bed height before cutting any material for this build rather than trusting a number from someone else's setup.

Step 1: Measure and Plan the Slot

Measure your bed's working height off the enclosure floor, and measure the thickness of the material you plan to run through most often (3mm plywood and 3mm acrylic are common defaults — plan the slot for your thickest expected stock plus a couple of millimeters of clearance). Mark the slot location on the rear or side panel at the same height as the bed surface, centered where your material will realistically run, and keep it as narrow as you can while still comfortably clearing your maximum stock thickness — a slot that's too generous lets smoke and light escape more than necessary.

Step 2: Cut the Slot

For a sheet-metal or acrylic enclosure panel, mark the slot and cut it with a rotary tool or jigsaw with a metal-cutting blade, then file or sand the edges smooth — a laser cutter's own bed can ironically be used to cut the slot in the removed panel if you take the panel off and it fits your work area, which is a satisfying way to bootstrap the project. Deburr thoroughly; sheet metal edges left sharp are a real cut hazard when you're feeding material through repeatedly.

Step 3: Build the External Riser

The riser is simply a stand that holds your outgoing material at bed height outside the machine. Build it from extruded aluminum profile or from laser-cut plywood ribs, sized so the top surface sits flush with your measured bed height. Add a smooth top surface — UHMW tape, a strip of laminate, or a roller bar — so material slides through without catching, which matters more than it sounds like once you're repositioning a long board multiple times during a single job.

• Cut two or more support legs to the exact riser height (bed height minus the thickness of the top surface material)
• Mount a crossbar or platform across the legs, wide enough to support the material without sagging over the unsupported span
• Add a fence or guide rail along one edge so material tracks straight and doesn't drift sideways between tiles — drift here is what causes visibly misaligned seams in the final cut
• Level the riser to the bed with shims if your shop floor isn't perfectly flat, and recheck it any time you move the machine or the riser

Step 4: Add Light and Smoke Containment

An open slot lets both stray laser light and smoke escape, which matters for both eye safety and air quality in the room. Hang a heavy fabric curtain (welding curtain material works well and is rated for the purpose) over the slot opening on the inside, cut with a slit for the material to pass through — it blocks direct view of the beam path without interfering with material feed. Keep your fume extraction running as normal; a pass-through slot doesn't change your ventilation requirements, and if anything you want slightly negative pressure in the enclosure so smoke is pulled in rather than pushed out through the gap.

Step 5: Tiling a Job in Software

In LightBurn, use the "Cut Selected Graphics" workflow combined with a manual offset: cut the first tile, note your machine's current X/Y position, move the physical material by a known, precisely measured distance (use a fence stop or a marked reference point on the riser to make repeats exact), then shift your design in software by that same distance before cutting the next section. Consistency in your physical stop is what keeps the seams invisible — a piece of tape or a clamped block on the riser as a hard stop removes the guesswork from "how far did I actually move it."

Safety Notes

Never reach into the slot while the laser is running, and never leave the machine unattended mid-tile with material hanging out through an open enclosure — an enclosed machine's safety benefit is partly defeated by an open pass-through, so treat the room the same way you would an open-frame laser: no bystanders, laser safety glasses rated for your machine's wavelength within reach, and a fire extinguisher nearby. Long material extending from the machine is also a physical trip and impact hazard in a shared shop space — flag it clearly or block off the area while a job is running.

Parts List

• - [Welding curtain or fire-resistant fabric curtain](https://www.amazon.com/s?k=welding+curtain+fire+resistant&tag=42308b-20)
• - [80/20-style aluminum T-slot extrusion, 20x20mm](https://www.amazon.com/s?k=2020+aluminum+t-slot+extrusion&tag=42308b-20)
• - [T-slot corner brackets and fasteners](https://www.amazon.com/s?k=2020+t-slot+corner+bracket+kit&tag=42308b-20)
• - [UHMW slide tape](https://www.amazon.com/s?k=UHMW+slide+tape&tag=42308b-20)
• - [Adjustable leveling feet](https://www.amazon.com/s?k=adjustable+leveling+feet+M8&tag=42308b-20)
• - [Rotary tool with metal cutting wheel](https://www.amazon.com/s?k=rotary+tool+metal+cutting+wheel+kit&tag=42308b-20)
• - [Metal file and deburring set](https://www.amazon.com/s?k=metal+file+deburring+tool+set&tag=42308b-20)
• - [Bar clamps for jig alignment](https://www.amazon.com/s?k=bar+clamps+6+inch&tag=42308b-20)

Once it's dialed in, a pass-through slot turns a laser cutter with a modest bed into a machine that can handle full sheet goods and long stock, one measured tile at a time. The setup work is entirely mechanical — get the riser height right, keep your physical stops consistent, and the seams between tiles disappear into the finished piece.